There is currently great interest in employing devices to curb, monitor and control the use and operation of equipment, and particularly motor vehicles, by those under the influence of alcohol. Current technology provides devices that obtain breath samples of a driver, measure the concentration of alcohol in the breath sample, correlate that concentration to a blood alcohol concentration (BAC) and use the determined value to monitor the driver's condition and control his ability to operate the vehicle. Often the sensor system is connected to an interlock for the vehicle to prevent the vehicle from being started if the BAC is over a certain level, or to issue a warning if the vehicle is already in operation.
To insure consistency of breath samples, systems often use a small pump to pull a breath sample into the sensing chamber where the alcohol concentration is measured. The pump is usually a solenoid pump, which is prone to failure. If the pump fails, a proper breath sample is not drawn into the chamber, and accordingly the output of the alcohol sensor is not an accurate reflection of the condition of the user's breath sample intended to be obtained.
It is accordingly the purpose of the present invention to provide a method of monitoring the operation of such a solenoid pump to insure proper operation and thus the proper receipt of a breath sample by the breath sampling and sensing system. A further purpose of the invention is to provide such a method that can interface with other aspects of the sensing procedure to improve the reliability and performance thereof.